The GCN2 eIF2α Kinase Is Required for Adaptation to Amino Acid Deprivation in Mice

Abstract

The GCN2 eIF2α kinase is essential for activation of the general amino acid control pathway in yeast when one or more amino acids become limiting for growth. GCN2's function in mammals is unknown, but must differ, since mammals, unlike yeast, can synthesize only half of the standard 20 amino acids. To investigate the function of mammalian GCN2, we have generated a Gcn2 ^−/− knockout strain of mice. Gcn2 ^−/− mice are viable, fertile, and exhibit no phenotypic abnormalities under standard growth conditions. However, prenatal and neonatal mortalities are significantly increased in Gcn2 ^−/− mice whose mothers were reared on leucine-, tryptophan-, or glycine-deficient diets during gestation. Leucine deprivation produced the most pronounced effect, with a 63% reduction in the expected number of viable neonatal mice. Cultured embryonic stem cells derived from Gcn2 ^−/− mice failed to show the normal induction of eIF2α phosphorylation in cells deprived of leucine. To assess the biochemical effects of the loss of GCN2 in the whole animal, liver perfusion experiments were conducted. Histidine limitation in the presence of histidinol induced a twofold increase in the phosphorylation of eIF2α and a concomitant reduction in eIF2B activity in perfused livers from wild-type mice, but no changes in livers from Gcn2 ^−/− mice.

We thank Mark Magnuson and Cathy Pettepher for help in establishing the mouse Gcn2 knockout strain and Christopher Wright for providing the TL1 129 SvEvTac lambda genomic library. We thank Scott Myers, Keri Merritt, Zhao Lin, Rui Peng, and Adam Harris for technical assistance in isolation and characterization of the Gcn2 gene and Gcn2 knockout mice.

This work was supported by the Culpeper Foundation; the Ingram Cancer Center and Clinical Nutrition Research Unit of the Vanderbilt University School of Medicine; the Pennsylvania State University; and National Institutes of Health grants GM56957 to D.R.C., DK13499 to L.S.J., and GM49164 and GM643540 to R.C.W.